Collagen has been used as an implantable biomaterial for more than 50 years. The collagen used for biomedical implants is either derived from animals (e.g., cows, pigs, horses) and humans, or it is manufactured in vitro using recombinant engineering. It is known to be biocompatible and is resorbed and remodeled like natural tissues, via cellular and enzymatic processes. Conventional collagen implants typically have been made of highly porous, reconstituted bovine (i.e., cow) collagen. These collagen implants are commercially sold to surgeons as rectilinear sheets with uniform thicknesses and porosity. Their low density and high porosity make these collagen membranes supple and conformable. Unfortunately they therefore have inadequate tensile strength and stiffness, particularly after wetting with saline or blood, for use as a containment device in surgical applications.
Bone is the body's primarily structural tissue; consequently it can fracture and biomechanically fail. Fortunately, it has a remarkable ability to regenerate because bone tissue contains stem cells which are stimulated to form new bone within bone tissue and adjacent to the existing bone. Boney defects regenerate from stem cells residing in viable bone, stimulated by signally proteins, and multiplying on existing cells or on an extracellular matrix (i.e., trellis). Like all tissues, bone requires support via the vascular system to supply nutrients and cells, and to remove waste. Bone will not regenerate without prompt regeneration of new blood vessels (i.e., neovascularization), typically with the first days and weeks of the regenerative cascade.
Various attempts have been made in the past to stimulate or augment bone regeneration by introducing a bone regenerating material proximate a deteriorated bone structure. Such efforts have met with very limited success, however, because they have not been able adequately to control the placement of the bone regenerating material and thus guide the development of new or additional bone. Measures undertaken to control the placement of the bone regenerating material may hinder cell ingrowth and formation of blood vessels needed for development of additional bone and thus impede the desired bone regeneration. Thus, despite considerable efforts of the prior art, there has remained a long felt need for better methods of tissue augmentation, especially for bone regeneration or augmentation.